We are investigating fast (msec) and localized (micron-sized) calcium transients or ~sparks~ within developing rat myocytes using two-photon excitation of various fluorescent calcium ion indicators. A quantitative analysis of calcium variations suggests that these sparks arise from triad like structures (excitation_contraction units) that form very early on in muscle development (approximately embryonic day 6). Using a image analysis and visualization package available through the theory center here at Cornell, we have automated spark identification and counting. By analyzing spark probablilities in relation to morphological features, we have found that sparks are twice as likely to originate from the membranous regions surrounding nuclei and specific nuclei are extremely active. These findings may have relevance to the highly heterogeneous, nucleus specific and calcium regulated mRNA expression shown by other researchers. The sparks may also be involved in organizing the complex internal membrane system within striated muscle. We plan to continue our research along these lines. A manuscript of myocyte spark characterization is currently under preparation.